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標題: | 複合式儲存設備之設計與軟體支援 Design and Software Support of Hybrid Storag Devices |
作者: | Hao-Hsiang Chang 張皓翔 |
指導教授: | 洪士灝(Shih-Hao Hung) |
關鍵字: | 儲存虛擬化,複合式儲存裝置,磁碟快取,固態硬碟, Storage Virtualization,Hybrid Storage,Disk Cache,Device-Mapper,ramdisk,SSD, |
出版年 : | 2009 |
學位: | 碩士 |
摘要: | 近年來,由於儲存科技在減低磁碟的搜尋時間方面並沒有顯著的進步,使得CPU與磁碟裝置間的效能鴻溝有逐漸拉大的趨勢。有許多研究方法嘗試解決此一問題,例如在磁碟中加入內建的快取、使用預先提取(prefetching),採用固態硬碟或是ramdisk,還有作業系統中也有包含針對區塊式輸出入子系統(block IO subsystem)效能最佳化的機制,例如分頁快取(page cache) 和偵測循序IO的預先提取(read-ahead prefetching)。然而,製造成本或是資料一致性、安全性和省電也是重要的的考量因素。本篇論文以Linux kernel提供的device-mapper為基礎,提出一個採用ramdisk或固態硬碟做為磁碟快取,可參數化的儲存虛擬化機制。使用者可以自動地使用到高速的儲存裝置而不需將經常使用的資料由低速的裝置搬移到高速的裝置。
我們選擇了數個benchmark評估提出的機制,在Postmark的測試下,使用複合式儲存裝置的平均磁碟存取時間較僅傳統硬碟可以得到2.92倍的效能改進。我們亦實作了一個追蹤驅動式的模擬器來幫助使用者搜尋適合應用程式的最佳參數組合。本模擬工具透過Linux上的磁碟IO追蹤工具blktrace來模擬應用程式其工作負載(workload)的磁碟存取樣式在多種快取的參數組合下的效能。在真正購買之前,使用本模擬工具可以有效率地評估複合式儲存裝置的效能,同時也能節省許多花費在系統安裝及測試工作負載的時間。 In the recent years, the gap between the CPU performance and the hard disk drive performance becomes larger as the technology has not been able to reduce the disk seek time signi cantly. Many research works try to bring this gap closer, e.g. built-in disk cache, data prefetch, ramdisk and solid-state disks, and optimizations in the OS for block IO devices. However, other issues such as the manufacturing cost, the consistency and safety of data, and power consumption are also important concerns. In this thesis, we propose a storage virtualization mechanism to handle hybrid random-access storage devices made with solid-state disks, ramdisks, and hard disks. By implementing a con gurable, software cache driver based on the Linux device-mapper, the users can automatically take the advantage of the faster disk without the need to move frequently-used data from a slower storage device onto a faster storage device. We used several benchmarks to evaluate the proposed scheme. In the postmark benchmark, the average disk access time of our hybrid storage device was improved by 292% compared to the hard disk only. For finding the optimal con figuration for a particular application, we developed a trace-driven simulator to explore the search space. The simulator works with blktrace, an IO trace collection tool available on Linux platform, to simulate the disk access pattern of an application with a variety of cache con figurations. With the simulation tool, the performance with a hybrid storage device can be evaluated effectively before the actual purchase. Meanwhile, the time needed for installing the storage system and experimenting with the workload can also be saved. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/45611 |
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